The underlying condition of gout is hyperuricemia and, after remission of the gout attack, remedies to improve hyperuricemia are carried out. The therapeutic agents for hyperuricemia are broadly divided into a uricosuric agent and uric acid synthesis inhibitor (xanthine oxidase inhibitor), and are selected appropriately depending on the state and degree of the condition.
The xanthine oxidase (XOD) inhibitors include 2-phenylthiazole derivatives (PTLs 1 to 6, NPL 1), 3-phenylisothiazole derivatives (PTLs 7 and 8), phenylpyrazole derivatives (PTL 9 to 11), 2-phenyloxazole derivatives (PTL 12), and phenyl-heteroaryl derivatives (PTL 13). The production processes described in the patent literatures cited in PTLs 1 to 12 are those wherein heterocyclic rings are formed by production processes comprising a series of consecutive reactions and, thus, involve a large number of steps. The production process described in PTL 13 is a process wherein the skeleton is formed by direct coupling of a phenyl ring with a heterocyclic ring and, thus, involves a small number of steps. However, in this process, it is necessary to prepare boron compounds and therefore results in a higher cost. Thus, this process is not yet satisfactory from a standpoint of a low-cost production process involving a small number of steps.
As a process to bind a C—H bond on a heterocyclic ring directly to a phenyl ring without the use of boron compounds, there have been reported coupling reactions by using, as a catalyst, palladium (NPLs 2 to 10), rhodium (NPL 11), iridium (NPL 12), copper (NPL 13), nickel (NPL 14 and 15), cobalt (NPL 16), palladium-copper (NPL 17 to 19), and palladium-silver (NPL 20). Among them, the production process using a nickel catalyst is related to a synthetic process for a phenyl-substituted heterocyclic derivative which is a xanthine oxidase (XOD) inhibitor (NPL 9). However, there has been reported no example where a phenyl-substituted heterocyclic derivative of the present invention was synthesized by using a metal catalyst other than the nickel catalyst. In addition, none of the reactions is satisfactory from a standpoint of substrate restriction, cost, and yield.